feat: suggest the most similar task name when a given task does not exist

errors.go

@@ -13,11 +13,20 @@ var (
 )
 
 type taskNotFoundError struct {
-	taskName string
+	taskName   string
+	didYouMean string
 }
 
 func (err *taskNotFoundError) Error() string {
-	return fmt.Sprintf(`task: Task %q not found`, err.taskName)
+	if err.didYouMean != "" {
+		return fmt.Sprintf(
+			`task: Task %q does not exist. Did you mean %q?`,
+			err.taskName,
+			err.didYouMean,
+		)
+	}
+
+	return fmt.Sprintf(`task: Task %q does not exist`, err.taskName)
 }
 
 type taskInternalError struct {

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/mattn/go-zglob v0.0.3
 	github.com/mitchellh/hashstructure/v2 v2.0.2
 	github.com/radovskyb/watcher v1.0.7
+	github.com/sajari/fuzzy v1.0.0
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.8.0
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c

go.sum

@@ -26,6 +26,8 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/radovskyb/watcher v1.0.7 h1:AYePLih6dpmS32vlHfhCeli8127LzkIgwJGcwwe8tUE=
 github.com/radovskyb/watcher v1.0.7/go.mod h1:78okwvY5wPdzcb1UYnip1pvrZNIVEIh/Cm+ZuvsUYIg=
 github.com/rogpeppe/go-internal v1.8.1 h1:geMPLpDpQOgVyCg5z5GoRwLHepNdb71NXb67XFkP+Eg=
+github.com/sajari/fuzzy v1.0.0 h1:+FmwVvJErsd0d0hAPlj4CxqxUtQY/fOoY0DwX4ykpRY=
+github.com/sajari/fuzzy v1.0.0/go.mod h1:OjYR6KxoWOe9+dOlXeiCJd4dIbED4Oo8wpS89o0pwOo=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

help.go

@@ -78,7 +78,7 @@ func (e *Executor) tasksWithDesc() (tasks []*taskfile.Task) {
 	return
 }
 
-// PrintTaskNames prints only the task names in a Taskfile.
+// ListTaskNames prints only the task names in a Taskfile.
 // Only tasks with a non-empty description are printed if allTasks is false.
 // Otherwise, all task names are printed.
 func (e *Executor) ListTaskNames(allTasks bool) {

setup.go

@@ -17,6 +17,8 @@ import (
 	"github.com/go-task/task/v3/internal/output"
 	"github.com/go-task/task/v3/taskfile"
 	"github.com/go-task/task/v3/taskfile/read"
+
+	"github.com/sajari/fuzzy"
 )
 
 func (e *Executor) Setup() error {
@@ -28,6 +30,8 @@ func (e *Executor) Setup() error {
 		return err
 	}
 
+	e.setupFuzzyModel()
+
 	v, err := e.Taskfile.ParsedVersion()
 	if err != nil {
 		return err
@@ -85,6 +89,21 @@ func (e *Executor) readTaskfile() error {
 	return err
 }
 
+func (e *Executor) setupFuzzyModel() {
+	if e.Taskfile != nil {
+		model := fuzzy.NewModel()
+		model.SetThreshold(1) // because we want to build grammar based on every task name
+
+		var words []string
+		for taskName := range e.Taskfile.Tasks {
+			words = append(words, taskName)
+		}
+
+		model.Train(words)
+		e.fuzzyModel = model
+	}
+}
+
 func (e *Executor) setupTempDir() error {
 	if e.TempDir != "" {
 		return nil

task.go

@@ -16,6 +16,7 @@ import (
 	"github.com/go-task/task/v3/internal/templater"
 	"github.com/go-task/task/v3/taskfile"
 
+	"github.com/sajari/fuzzy"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -51,7 +52,8 @@ type Executor struct {
 	Output      output.Output
 	OutputStyle taskfile.Output
 
-	taskvars *taskfile.Vars
+	taskvars   *taskfile.Vars
+	fuzzyModel *fuzzy.Model
 
 	concurrencySemaphore chan struct{}
 	taskCallCount        map[string]*int32
@@ -68,7 +70,12 @@ func (e *Executor) Run(ctx context.Context, calls ...taskfile.Call) error {
 		if !ok {
 			// FIXME: move to the main package
 			e.ListTasksWithDesc()
-			return &taskNotFoundError{taskName: c.Task}
+
+			didYouMean := ""
+			if e.fuzzyModel != nil {
+				didYouMean = e.fuzzyModel.SpellCheck(c.Task)
+			}
+			return &taskNotFoundError{taskName: c.Task, didYouMean: didYouMean}
 		}
 		if t.Internal {
 			e.ListTasksWithDesc()

variables.go

@@ -24,7 +24,11 @@ func (e *Executor) FastCompiledTask(call taskfile.Call) (*taskfile.Task, error)
 func (e *Executor) compiledTask(call taskfile.Call, evaluateShVars bool) (*taskfile.Task, error) {
 	origTask, ok := e.Taskfile.Tasks[call.Task]
 	if !ok {
-		return nil, &taskNotFoundError{call.Task}
+		didYouMean := ""
+		if e.fuzzyModel != nil {
+			didYouMean = e.fuzzyModel.SpellCheck(call.Task)
+		}
+		return nil, &taskNotFoundError{taskName: call.Task, didYouMean: didYouMean}
 	}
 
 	var vars *taskfile.Vars